mcfadden. >> tatyana mcfadden of the united states. >> reporter: and the first thing tatyana after winning in boston as the shock of the attack set in, was to head for the marathon in london. >> people are like, "why are you going to be running ?" i'm dedicating the whole weekend to the people in boston, and i'm running for them. >> reporter: every marathoner knows that absolute security at these massive urban races can never be guaranteed, and while the london marathon has never been attacked and there's plenty of experience here with policing public events, there's also plenty of experience with carn annual in public places. instigated by islamic terrorists in the subway bombings of july 2005. and by the irish republican army on several occasions. is there a little bit of fear involved now that one marathon has been attacked? >> i don't worry. i-- you can't live your life in fear. i mean, anything could happen anywhere. >> reporter: but the closing stretch of a marathon is not just anywhere. london's is in front of buckingham palace. the wheelchair marathoners say they have a double moti